I changed the value in INTERNALDESCRIPTION_EN because my database does not support chinese characters but it works in the same way (I assumed your file is registered in UTF-8, if it is not the case then change the character set in line 9).

I searched on the web and the constant answer I found is what I thought: the NVARCHAR2 or NCLOB datatypes are supported by no XML function.
Your only solution is to recreate your database in AL32UTF8 character set and use the standard CLOB/VARCHAR2 datatypes.

I don't think it is (exactly) the same thing as in this bug the database is also in Unicode ("could not convert from encoding UTF-8 to UCS2") mine is not (WE8MSWIN1252) and I also tried it in 11.2.0.1 and got the same error (was in 10.2.0.4).
I will upgrade my database to 10.2.0.5 and 11.2.0.3 and restest (but it is my laptop db and so not my priority now but I keep this in mind).
What is your version and database character set?